normalization
normalization is basically used to decomposes the data when the redundancy is occur . its an primary use of the database management system.
basically 3 normal forms enough to build an data base system .
1.first normal form
2.second normal form
3.third normal form
first normal form
the table is said to be in first normal form it satisfy s the following steps
1.table must have the atomic values that means single values.
2.primary key identified by the table.
3.all columns of the table defined on primary key
as shown in below
table : student details
primary key : student id
student id student name branch
s1 rainy computer science
s 2 james electrical
second normal form
the table is said to be in second normal form it should satisfy the following rules
1.it should satisfy s the first normal form rules
2.it does not contain the partial dependency s
table name : project details
primary key : project id + student id
project id student id student name project name
p1 s1 james e learning
p2 s2 john e books
p3 s3 prema space research
the above table is not in second normal form its violets the second rule. it has partial dependency s
that means it has two primary keys so this is not in second normal form . above table can be divided into 3 ways
1) table name : project details
primary key : project id
project id projcet name
p1 e learning
p2 e books
p3 space research
2) table name : student details
primary key : student id
student id student name
s1 james
s2 john
s3 prema
3) table name : project details
primary key : student id + project id
student id project id project name
s1 p1 e learning
s2 p2 e books
s3 p3 space research
all these tables are in 3rd normal form
third normal form
the table is said to be in third normal form it should satisfy the following rules
1.it satisfy the 2nd normal form
2.table does not have the transitive dependency s . that means any of column of the table does not depend upon the non primary key column
table name : project details
primary key : student id
student id student name project id project name
s1 stefen p1 water plant
s2 shreenita p2 snow scating
s3 roja raman p3 texting
above table is not in third normal form in that table project name depending on non primary key column project id . so it is having partial dependency s . the table can be divided into different ways as shown in below .
1) table name : student details
primary key : student id
student id student name
s1 stefen
s2 shreenita
s3 roja raman
2) table name : project details
primary key : project id
project id project name
p1 water plant
p2 snow scating
p3 texting
table name : student details
primary key : student id
student id project id student name
s1 p1 stefen
s2 p2 shreenita
s3 p3 roja raman
etc...
all these tables are in 3rd normal form....................
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